Garson Kanin’s play “Born Yesterday” was born quite a few yesterdays ago. Unlike other works of similar mid-20th-century vintage, it hasn’t aged especially well.

That lamentable fact is demonstrated by the polished and well-cast but ultimately disappointing Moonlight Stage Productions revival that just opened at Vista’s Avo Playhouse.

The show has its moments, but the play’s sudden bursts of sanctimony and its dated, sometimes jokey mode of dealing with such subjects as domestic violence can make it uncomfortable as comedy and unconvincing as drama.

The issue begins right at the play’s center, with the impossibly ditsy Billie Dawn, the former chorus girl and current arm candy whose Eliza Doolittle-lite intellectual awakening drives the story.

Billie (Jessica John) somehow has become an adult without learning that London is in England and that there’s something called a Supreme Court. When Harry Brock (David Cochran Heath), her rich clod of a boyfriend, hires a writer named Paul Verrall (Brian Mackey) to culture her so as to grease his shady D.C. dealings, the pair find common ground in standing up for the common people.

If you’ve never seen the 1946 play (or the 1950 movie adaptation starring Judy Holliday), you’ll realize soon enough — maybe with a fidgeting sense of dismay — that yes, this will be the story of a simple soul who ultimately teaches the smart people a thing or two about what’s really important.

Thanks, of course, to The Love of a Good Man.

If the characterization of Billie as a sexy simpleton — “I’m stupid, and I like it,” she says near the top of the show — carries a whiff of the chauvinistic (at least by today’s standards), John still plays her with an expert comic blend of the abrasive and the appealing.

Even when she’s silently mouthing the numbers she’s counting off during a game of gin rummy, you can just about read the shapes of those hard New Yawk vowels (“eight, noyne …”).

Heath, an accomplished veteran of decades’ worth of shows at Lambs Players Theatre, makes a welcome return to the stage with “Born Yesterday.” Yet the role of the boorish, vulgar and at times violent Harry can feel like a naggingly ill fit for the actor, who seems in his wheelhouse with more refined (or at least benign) characters.

“He has always lived at the top of his voice,” the melancholy lawyer Ed Devery (an effective Jim Chovick) says of Harry, and in this case the sentiment is a bit too true: It’s as if Heath is trying to force a sense of coarseness through sheer volume.

Director Jason Heil’s tentative-feeling production (with a richly detailed hotel-suite set by North Coast Rep’s Marty Burnett) certainly doesn’t lack for talent. There’s solid work from Mackey (who still comes off as a bit callow for the part), Danny Campbell as an ethically pliable senator, Paul Morgavo as Harry’s put-upon cousin and guy Friday, and others.

But this story of finding enlightenment seems to have lost some of its own luster.